Friday, February 8, 2013

It Literally Takes Your Breath Away

Hayley Chilton

Figure 1. A mountain climber above the clouds.

You have been training for
this day for a long time. Climbing local hills in your home town as you build up your
endurance to a point where you feel ready to take on the challenge of a large
mountain. Now imagine you’ve spent two
days climbing Mt. Whitney and you can see the summit. You are at 14,000 feet above sea
level and yet the last couple yards seem impossible. All of a sudden you feel
as though you had one too many shots at the bar. You’re seeing double and
gasping for air, as if someone is sitting on your chest. You feel dizzy and
have to sit down after taking a step. Aside from the shifting daily temperature
extremes and decreased humidity, why is this happening to you?

The answer is simple; it’s
the air pressure at high altitude. As you ascend up into the mountains the
pressure of the atmosphere decreases relative to atmospheric pressure at sea
level. However, the percentage of oxygen in the air doesn’t really change.
Whether you are at sea level, or 500 feet from the summit of Mt. Whitney the
air you are breathing contains about 21% oxygen. So why does it feel so hard to
catch your breath at higher elevations? Well, as I mentioned before, the
decrease in atmospheric pressure means that there are fewer molecules present…basically
there is less “air.” Therefore while the ratio of oxygen relative to all of the
other gases that make up the air we breathe doesn’t change, each breath we take
contains less oxygen, which is why at higher altitudes you might feel as though
you are breathing through a straw.

Yet, we see people around the
world who live in regions of high elevation and seem to lead relatively
normal lives. In fact, Benjamin Levine
and James Stray-Gundersen found that acclimatization to moderate altitude when
combined with lower altitude training enhances athletic performance in
competitive athletes. How is this possible given that we just discussed how
breathing is more difficult the higher you are above sea level? Well, given
time, your body is able to acclimate to these conditions. Sensory organs called
carotid bodies can detect lack of oxygen in your blood and immediately alert
the brain to regulate/elevate breathing to restore oxygen levels. Your body also increases red blood cell production, which inadvertently increases your body’s ability
to transport oxygen through your bloodstream. This is because more hemoglobin,
an oxygen-binding protein found on your red blood cells, is available to bind oxygen. Moreover, your heart is pumping
faster to decrease the amount of time it takes oxygenated blood to circulate
through your body…so in short, you have more efficient blood and circulation!

However, despite all of this,
oxygen deprivation can be very serious and can elicit several additional physiological
changes in your body. First of all,
your body increases its metabolic rate due to increased energy expenditure
required to maintain all of these compensatory functions. Not only will this
cause your body to burn more carbohydrates and fat to replace depleted energy
levels, but a study by Matthias Tschop and his colleges found that at higher
altitudes people also have higher levels of leptin, a hormone that regulates
energy homeostasis and appetite. Therefore, at higher altitudes, people also
experience a loss of appetite without even being aware of it. This can be
detrimental due to the increased energy demands your body has to function at
higher elevations.

As
mentioned earlier, the decreased humidity and low air pressure often
experienced by hikers can quickly lead to dehydration. In combination
with increased respiratory function, dehydration can contribute to the onset of
respiratory alkalosis. Respiratory alkalosis is a condition affecting the pH of
your blood. When your breathing rate elevates, the relative amount of carbon
dioxide in your blood stream is depleted as you try to maximize oxygen intake.
In the long run, this will inevitably lead to a decreased respiratory rate and
you will not be able to continue at the rate needed to maintain adequate oxygen
levels. Your breathing will slow down and become more erratic, sometimes stopping
for several seconds at a time until carbon dioxide levels return to normal.

Acute Mountain Sickness (AMS) is an altitude-related
neurological condition. As with
most forms of altitude sickness, AMS can be treated with over the counter drugs,
but not cured without acclimatization or descent to lower elevations. Symptoms
include anything from headaches to loss of coordination and
trouble thinking.

Figure 3. What is high altitude?

Meanwhile, High Altitude
Pulmonary Edema, HAPE, is a condition characterized by fluid leakage from your
blood vessels into your lungs! When oxygen levels are low, your blood vessels
often constrict causing your blood pressure to elevate, forcing fluid out of
spaces in vessel walls. Your chest will become tight making it
harder to breath and the fluid buildup in your lungs will cause you to
wheeze/cough persistently. If that wasn’t bad enough other side effects include
confusion, amnesia, and possibly even loss of consciousness, so
it is very important to be aware of your symptoms!

But, even more serious than
HAPE is HACE, High Altitude Cerebral Edema, which manifests if blood vessels in
your brain begin to leak fluid into the surrounding tissue. Your brain is your
body’s control center; it helps regulate all of your organs, hormones,
extremities and biological processes. Therefore, compromising any of these
functions can lead to serious complications or death. HACE is similar to HAPE
in that people who have it may experience symptoms that alter their motor
control or cognitive ability. Needless to say, seeking immediate help is
imperative. Descending to lower elevations may help you to restore full mental
capacity, however it can take up to several weeks to feel like you have your
bearings back.

Figure 4. Summary of symptoms.

A
study by Fayed and his colleges revealed that HACE could have extensive
long-term neurological damage with respect to your overall mental capacity,
memory and coordination. In this study Fayed examined MRI brain scans of 12
professional and 23 amateur climbers after they had returned from high altitude
expeditions on Mt. Kilimanjaro (Tanzania, 19,341 ft.), Mt. Aconcagua
(Argentina, 22,837 ft.), Mt. Blanc (France, 15,781 ft.) or Mt. Everest (Nepal,
29,029 ft.). Of the 12 professionals and one amateur climber that attempted to
conquer Mt. Everest, brain damage in all but one professional climber was seen
upon their return. Based on these results Fayed concluded that
high altitude climbing results in irreversible brain damage. While acclimatization to higher elevations can minimize
these consequences, it cannot negate the side effects completely. So, if you
are planning on conquering one of these great mountains, just keep in mind that
your brain will probably not be in the same condition that it was before you
left.

Figure 5. Several hikers climbing Mt. Everest

Wow!
I know that was a lot to take in, but hopefully you were able to learn just how
important it is to be aware of your body and how you’re feeling when you’re up
at high elevation. Do not let this discourage you from taking on the challenge,
because the sense of accomplishment along with the breath taking views make the
physical struggle of the climb all worth it. Just be smart about it. If you
experience any of these symptoms, stay put or descend immediately. Altitude
sickness is nothing to mess around with. These symptoms can manifest themselves
in even the most fit of athletes. Drink plenty of water to avoid
dehydration…and most importantly, give your body time to acclimate! Happy
hiking!

2 comments:

Reading "Into Thin Air" was enough to cure me from ever wanting to take on the highest peaks. Climbing Mt. Everest sounded like 6 weeks of being cold and unable to breathe, and that's a best case scenario. The glory is pretty impressive, but toss in all the complications from altitude like HAPE and HACE and I'll pass. Interesting as usual Hayley.

Sooo this blog has definitely helped to solidify my decision to never hike Mt. EVEREST, not that I was ever really going to, but now knowing the dangers of HAPE and HACE on top of the fear of coming across one of the approximately 120 dead bodies already up there, NO THANK YOU!!